C i6 3 ] 
The diminution of the quantity of air in which a 
candle, or brimftone, has burned out, is various ; 
but I imagine that, at a medium, it may be about 
one fifteenth, or one fixteenth, of the whole; about 
one third as much as by animals breathing it as long 
as they can, by animal or vegetable fubftances 
putrifying in it, by the calcination of metals, or by 
a mixture of fteel filings and pounded brimftone 
{landing in it. 
I have fometimes thought, that flame difpofes the 
common air to depofit the fixed air it contains ; for 
if any lime-water be expofed to it, it immediately 
becomes turbid. This is the cafe, when wax candles, 
tallow candles, chips of wood, fpirit of wine, aether, 
and every other fubftance which I have yet tried, 
except brimftone, is burned in a clofe glafs veil'd, 
ftan ting in lime-water. This precipitation of fixed 
air (if this be the cafe) may be owing to fomething 
emitted from the burning bodies, which has a ftronger 
affinity with the other conftituent parts of the atmo- 
fphere. 
If brimftone be burned in the fame circum- 
ftances, the lime-water continues tranfparent, but 
ftill there may have been the fame precipitation 
of the fixed part of the air; but that, uniting with 
the lime and the vitriolic acid, it forms a felenetic fait, 
which is foluble in water. Having evaporated a 
quantity of water thus impregnated, by burning 
brimftone a great number of times over it, a whitifli 
powder remained, which had an acid tafte; but re- 
peating the experiment with a quicker evaporation, 
the powder had no acidity, but was very much like 
chalk. The burning of brimftone but once over a 
Y 2 quantity 
